The present invention relates to a method for fabricating a semiconductor device, and more particularly, to a method for forming an insulation layer in a semiconductor device.
As semiconductor devices have become highly integrated, spaces between gate patterns and line widths of gate patterns have narrowed. Thus, it has become difficult to secure spaces for forming contact openings during a landing plug contact hole process. A space of approximately 30 nm should be secured between gate patterns to maintain a contact opening in consideration of a line width variation during a gate process.
It may be difficult to form an insulation layer between gate patterns using a general deposition method because the space between the gate patterns is small. Thus, a borophosphosilicate glass (BPSG) layer having a sufficient level of gap-fill characteristic is used as the insulation layer. When using the BPSG layer as the insulation layer, a nitride-based layer having a thickness larger than a given thickness is generally needed to reduce impurities penetrating into the substrate.
Therefore, gate spacers for forming spacers on sidewalls of the gate patterns and cell spacers for reducing impurities in the BPSG layer penetrating into the substrate are formed after the formation of the gate patterns. However, applying both of the gate spacers and the cell spacers causes a thickness of the nitride-based layer formed between the gate patterns and over the substrate to become too large. Thus, a contact-not-open event may occur during a subsequent self-aligned contact (SAC) etch process, as denoted with a reference numeral 100 in FIG. 1. That is, due to characteristics of the SAC etch process using a selectivity between oxide and nitride, limitations may arise in etching if the thickness of the nitride-based layer is too large, causing the contact-not-open event to occur.
Forming the gate spacers and the cell spacers on the sidewalls of the gate patterns causes the space between the gate patterns to further narrow. Consequently, the gap-fill characteristic may be deteriorated when forming the insulation layer.